Trip mechanisms are frequently employed with rotary machines to reduce the speed thereof or to completely terminate the operation of the rotary machine upon the occurrence of an undesirable operating condition such as excessive shaft speed. One type of trip mechanism employs a Belleville spring having a plurality of weights secured thereto and which is mounted on the shaft of the rotary machine so as to rotate therewith. Rotary motion is typically transmitted from the shaft to the Belleville spring through the coaction of an auxiliary spring which is also of the Belleville type and which exerts an axial force on the main spring so as to push it against a support sleeve. This force, along with friction, normally prevents slippage between the main Belleville spring and the shaft. This arrangement does not always work, however. If oil gets onto the assembly and reduces the friction between the parts, slippage can occur. Also, if there is a sudden acceleration, the torque exerted as a result of the acceleration may overcome friction and slippage can occur. If the spring is slipping, it is not rotating at the same speed as the shaft and will not trip at the correct speed.